Chemical disorder reinforces magnetic order in ludwigite (Ni,Mn)(3)BO5 with Mn4+ inclusion

Crystals of ludwigite Ni2.14Mn0.86BO5 were synthesized by flux growth technique and contain Mn3+ and Mn4+. A possible mechanism of the manganese valence states stabilization has been proposed. The structural and magnetic characterization of the synthesized samples has been carried out in detail. The cations composition and Mn valence states of the crystal were determined using X-ray diffraction and EXAFS technique. The comparative analysis was carried out between the studied crystal and Ni2MnBO5 synthesized previously. Magnetic susceptibility measurements were carried out. The magnetic transition in the studied composition occurs at the 100 K temperature that is higher than in Ni2MnBO5 although the studied composition is more disordered. The calculations of the exchange integrals in the frameworks of indirect coupling model revealed strong antiferromagnetic interactions. The several magnetic subsystems existence hypothesis was supposed. The possible magnetic structure was suggested from the energies estimation for different ordering variants

Magnetic structure of Cu2MnBO5 ludwigite: thermodynamic, magnetic properties and neutron diffraction study

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.We report on the thermodynamic, magnetic properties and the magnetic structure of ludwigite-type Cu2MnBO5. The specific heat, low-field magnetization and paramagnetic susceptibility were studied on a single crystal and combined with powder neutron diffraction data. The temperature dependence of the specific heat and the neutron diffraction pattern reveal a single magnetic phase transition at T = 92 K, which corresponds to the magnetic ordering into a ferrimagnetic phase. The cation distribution and the values and directions of magnetic moments of ions in different crystallographic sites are established. The magnetic moments of Cu2+ and Mn3+ ions occupying different magnetic sites in the ferrimagnetic phase are pairwise antiparallel and their directions do not coincide with the directions of the principal crystallographic axes. The small value of the magnetic moment of copper ions occupying site 2a is indicative of partial disordering of the magnetic moments on this site. The magnetization measurements show a strong temperature hysteresis of magnetization, which evidences for field-dependent transitions below the phase transition temperature

Transformation of the concept of legal system in the conditions of globalisation

The purpose of the study is to identify the main trends and factors influencing the development of the theoretical concept of the legal system and possible categories derived from it. The methodological basis of the research is represented by such scientific methods as dialectical, logical, historical, predictive, systemic analysis and content analysis. This made it possible, in view of achievement of the said objective, to analyse the works of Russian and foreign comparativists, both the founders of modern comparative jurisprudence and novice researchers, as well as the materials of scientific conferences on the problem under investigation. The result of the study was the conclusion that the complex nature of the category “legal system” makes it possible to form a holistic picture of legal reality. At the same time, the result of the research depends on the criterion laid as a basis for this concept. The paper also substantiates the fact that presently one may observe a tendency towards a comprehensive understanding of the legal system, towards rejection of the formational approach in favour of the socio-cultural one, with regard for a number of other internal and external factors affecting the formation and functioning of the legal system. The novelty of the study was the conclusion that the concept of the legal system, as well as the categories derived from it, so far represent the basic theoretical function in formulating hypotheses, setting goals and objectives of comparative legal research. At the same time, the authors note that a unified approach to comprehending the essence, typology and classification of legal systems is objectively not possible in the conditions of multiple legal cultures and traditions of legal consciousness, which, ultimately, should be assessed as a positive stimulus for further research

Magnetic structure of Cu2MnBO5 ludwigite: thermodynamic, magnetic properties and neutron diffraction study

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.We report on the thermodynamic, magnetic properties and the magnetic structure of ludwigite-type Cu2MnBO5. The specific heat, low-field magnetization and paramagnetic susceptibility were studied on a single crystal and combined with powder neutron diffraction data. The temperature dependence of the specific heat and the neutron diffraction pattern reveal a single magnetic phase transition at T = 92 K, which corresponds to the magnetic ordering into a ferrimagnetic phase. The cation distribution and the values and directions of magnetic moments of ions in different crystallographic sites are established. The magnetic moments of Cu2+ and Mn3+ ions occupying different magnetic sites in the ferrimagnetic phase are pairwise antiparallel and their directions do not coincide with the directions of the principal crystallographic axes. The small value of the magnetic moment of copper ions occupying site 2a is indicative of partial disordering of the magnetic moments on this site. The magnetization measurements show a strong temperature hysteresis of magnetization, which evidences for field-dependent transitions below the phase transition temperature

Crystal Growth and Raman Spectroscopy Study of Sm_1–<i>x</i>La_<i>x</i>Fe₃(BO₃)₄ Ferroborates

Sm_1–<i>x</i>La_<i>x</i>Fe₃(BO₃)₄ (<i>x</i> = 0, 0.75) single crystals were synthesized using the flux method. The crystal nucleation procedure and flux parameters are reported. Conditions for growing the Sm_1–<i>x</i>La_<i>x</i>Fe₃(BO₃)₄ (<i>x</i> = 0, 0.75) single crystals are described. The prepared crystals were studied by Raman spectroscopy in the temperature range of <i>T</i> = 10–300 K. The spectral region corresponding to temperatures of <i>T</i> = 10–55 K, which involves the temperatures of the magnetic phase transition <i>T</i>_N = 32 K for <i>x</i> = 0 and <i>T</i>_N = 31 K for <i>x</i> = 0.75, was thoroughly analyzed. Anomalies related to the magnetic ordering established in both compounds were found. The main changes occur in the low-wavenumber region (up to 100 cm^–1), where the mode corresponding to magnon scattering arises. This mode is shown to have the internal structure indicative of the occurrence of unstable vibrations (40–80 cm^–1). The results obtained are analyzed by calculating the empirical lattice dynamics in Sm_1–<i>x</i>La_<i>x</i>Fe₃(BO₃)₄ with <i>x</i> = 0 and <i>x</i> = 1

Fixed-Point Models for Theories of Properties and Classes

There is a vibrant (but minority) community among philosophical logicians seeking to resolve the paradoxes of classes, properties and truth by way of adopting some non-classical logic in which trivialising paradoxical arguments are not valid. There is also a long tradition in theoretical computer science–going back to Dana Scott’s fixed point model construction for the untyped lambda-calculus–of models allowing for fixed points. In this paper, I will bring these traditions closer together, to show how these model constructions can shed light on what we could hope for in a non-trivial model of a theory for classes, properties or truth featuring fixed points

Role of Lipids of the Evergreen Shrub <i>Ephedra monosperma</i> in Adaptation to Low Temperature in the Cryolithozone

Lipids are the fundamental components of cell membranes and they play a significant role in their integrity and fluidity. The alteration in lipid composition of membranes has been reported to be a major response to abiotic environmental stresses. Seasonal dynamics of membrane lipids in the shoots of Ephedra monosperma J.G. Gmel. ex C.A. Mey. growing in natural conditions of permafrost ecosystems was studied using HPTLC, GC-MS and ESI-MS. An important role of lipid metabolism was established during the autumn-winter period when the shoots of the evergreen shrub were exposed to low positive (3.6 °C), negative (−8.3 °C) and extremely low temperatures (−38.4 °C). Maximum accumulation of phosphatidic acid (PA), the amount of which is times times greater than the sum of phosphatidylcholine and phosphatidylethanolamine (PC + PE) was noted in shoots of E. monosperma in the summer-autumn period. The autumn hardening period (3.6 °C) is accompanied by active biosynthesis and accumulation of membrane lipids, a decrease of saturated 34:1 PCs, 34:1 PEs and 34:1 PAs, and an increase in unsaturated long-chain 38:5 PEs, 38:6 PEs, indicating that the adaptation of E. monosperma occurs not at the level of lipid classes but at the level of molecular species. At a further decrease of average daily air temperature in October (−8.3 °C) a sharp decline of PA level was registered. At an extreme reduction of environmental temperature (−38.4 °C) the content of non-bilayer PE and PA increases, the level of unsaturated fatty acids (FA) rises due to the increase of C18:2(Δ9,12) and C18:3(Δ9,12,15) acids and the decrease of C16:0 acids. It is concluded that changes in lipid metabolism reflect structural and functional reorganization of cell membranes and are an integral component of the complex process of plant hardening to low temperatures, which contributes to the survival of E. monosperma monocotyledonous plants in the extreme conditions of the Yakutia cryolithozone